156 GASTROCH^NIDJE. 



V. iRus, Linnseus. 



Plate VII. figs. 1, 2, 3, and (animal) Plate G. f, 2. 



Donax Irits, Linn. Syst. Nat. ed. 12, p. 1128. — Pulteney, Hutchins Dorset, 

 p. 32.— DoNov. Brit, Shells, vol. i. pi. 29, f. 2.— Mont. Test. 

 Brit. pp. 108, 573. — Linn. Trans, vol. viii. p. 77. — Dorset Cat. 

 p. 34, pi. 12, f. 6 (badly).— TuRT. Conch. Diction, p. 43.— 

 Chemn. Conch. Cab. vol. vi. p. 271, pi. 26, f. 2G8, 269, 270.— 

 Pom, Test. Sicil.pl. 10, f. 1, 2, 3, and pi. 19, f. 25, 26.— Dillw. 

 Recent Shells, vol. i. p. 156. — Index Testaceolog. pi. 6, Donax, 

 f. 21. 

 Tellina Cornuliensis, Penn. Brit. Zool. ed. 4 (from Borlase's Cornwall, pi. 28, 



f. 23). 

 Cumiis foliatus. Da Costa, Brit. Conch, p. 204, pi. 15, f. 6, on the left. 

 Veneriipis Irus, Lam. Anim. s. Vert. ed. 2, vol. vi. p. 163. — Flem. Brit. Anim, 

 p. 451. — Brit. Marine Conch, p. 60. — Desh. Elem. Conch, pi. 

 12, f. 16, 17, 18,— Philippi, Moll. Sicil. vol. i. p. 21 ; and vol. 

 ii. p. 20 — Hanl. Recent Shells, p. 54. — Exped. Scient. Alge- 

 rie, Moll. pi. 66, f. 14 to 17 (animal). 

 Petricola friis, Turt. Dithyra Brit. p. 26, pi. 2, f. 14. 

 Ptdlastra Irus, Brown, Illust. Conch. G. B. p. 89, pi. 37, f. 9. 



No minute and prolonged investigation is demanded, for 

 the discrimination of this rock-borer from any of the 

 hitherto-found Testacea of our shores, the remarkable 

 lamellation of its surface, enabling us immediately to 

 separate it : the chief difficulty rests in discovering strictly 

 permanent characteristics which may distinguish it from 

 its foreign congeners, a few of which might easily be 

 reckoned by the inexperienced, as but aberrant varieties of 

 the same species. The shape is of course modified by that 

 of its habitation, but is typically subrhomboidal, at times 

 its length scarcely exceeds its breadth by one-fourth, more 

 usually, hoAvever, it nearly doubles it, and certain specimens 

 are even still more longitudinally produced. The more 

 beautiful live shells (as they are technically called) are 

 of a pure slightly translucent white ; such, however, are 

 rare, and indeed but few specimens comparatively are 

 taken with the animal in them. Most examples are of 

 an uniform opaque dirty-white, or pale drab, externally: 



